This is the most common input device for a computer. It is used to enter text and numeric data for processing. The design of the modern computer keyboard has it's origins in the first manually operated typewriters developed in the 18th century. A layout for the keys was developed that put the most frequently used characters undereath the outside 4 fingers of both hands. The keys inthe rows above and below the center row were placed to minimize the finger movement of the less frequently used characters. The layout is known as a Qwerty keyboard and if you will notice this is the first six characters of the top row to alphabetic keys.
Teletypes arrived in the early 1900's and borrowed from the typewriter for thier keyboard. A few additional special purpose keys were added to aid in the sending/receiving of text messages which was the machines purpose (replacing the telegraph).
With the advent of computers keyboards added more special keys such as cursor positiong, (up,down,left,right), the control key (ctl) and the alternate key
(alt), and funtion keys (F1 thru F12).